Resin compositions containing EVOH and a polyamide resin have a gas barrier property, oil resistance, and solvent resistance that are provided by the EVOH while having hot water resistance that is provided by the polyamide resin. They are suitable for packaging materials that are used for boiling or retort applications, for example Conventionally, molded articles (films, sheets, etc.) made of the aforementioned resin compositions are produced by melt molding with, for example, a melt extruder using pellets as a raw material with the pellets being obtained by heating and melting EVOH and a polyamide resin to mix them together and then forming this into pellets.
However, when EVOH, and a conventional polyamide resin are mixed in a molten state gels that are thermally deteriorated products are produced due to the contact therebetween and thereby pellets containing gels are formed. When such pellets are used as a raw material for molded articles besides the gels contained in the pellets, more gels are produced during melt molding. Accordingly a number of gels remain in the molded articles. Thus molded articles with sufficiently high quality cannot be obtained.
In order to solve such a problem, a method is proposed in which a polyamide resin with a specific composition is used and is dry-blended or pelletized together with EVOH. For instance, JP4 (1992)-114060A discloses a technique of using a polyamide resin that has been modified with acid anhydride, carboxylic acid, carboxylate ester, etc so that the content of the terminal amino groups is 30μ equivalents (eq)/g or less. In JP4(0992)-114060A, an improvement in the thermal stability during melt molding (an reduction in the amount of gels to be produced) is intended to be achieved. However, as indicated in the comparative examples to be described later, this technique does not provide a sufficiently high effect of improving the thermal stability, particularly in the case of pelletizing.
On the other hand, JP59 (1984)-081121A discloses a multilayered pellet having a core-sheath structure composed of a core layer and a sheath layer. The multilayered pellet disclosed in JP59 (1984)-81121A is a multilayered pellet containing an olefin-vinyl alcohol copolymer as the core layer and an olefin resin as the sheath layer. This multilayered pellet is formed as follows. That is, with a melt whose main component is an olefin-vinyl alcohol copolymer being used for a core and a melt whose main component is an olefin resin being used for a sheath, they are melt-extruded in the form of a strand and then this is cut after being cooled. Thus a multilayered pellet is formed. This method makes it possible to pelletize an olefin-vinyl alcohol copolymer that is difficult to be melt-extruded in the form of a strand by itself due to its low melt tension while allowing the pellets formed by the method to be prevented from absorbing water by using the olefin resin for the sheath layer.